we just encounted a situation in our game where one ally attacked Paris, but when the second moved and tried to attack in his move, the system would not allow it. I take it the game was written to only allow one city assault in a month, or is this a bug?

Marshall Ellis -> RE: city attacks (12/21/2011 2:18:20 PM)

This is normal. The only way an ally could participate would be through loaned forces (Thus receiving approval from first ally). We allowed this earlier but retracted due to potential gamesmenship of an ally grabbing the easy pickings of someone else's efforts.